Hi All, Its urgent.... Although, SIP 183 Session Progress is expected with SDP (industrial behavior), it may/may not have SDP and the UACs should be able to handle it. So, having no SDP in SIP 183 Session Progress may not cause a ringback problem if the UAC behaves based on the RFC specs. But i recently developed a application using PJSIP and tested it on the server all things working fine but the ringback is not coming means 180 ringing event is not noticed by the pjsip if there is no SDP in SIP 183 Session Progress. My server doesn't have SDP in the PJSIP. But the SDP is coming in the 180 Ringing packet, But in 180 Ringing packet the "received" parameter in the "via" feild is missing in my server case is it due to this that I am not capturing the 180 riniging event. If this is not the problem then PJSIP need to improve upon this. Regards: Ravi -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.pjsip.org/pipermail/pjsip_lists.pjsip.org/attachments/20090819/abb06b30/attachment.html>